We reiterate, in more details, our previous proposal of using quasiparticle interference to determine the pairing form factor in iron-based superconductors. We also present our functional renormalization group (FRG) results on LaFePO and Fe(Se,Te) superconductors. In particular, we found that the leading pairing channel in LaFePO is nodal $s_{\pm }$ with nodes on electron Fermi surfaces. For Fe(Se,Te) system we found fully gapped $s_{\pm }$ pairing with substantial gap anisotropy on electron Fermi surfaces and large gap is concentrated in regions with dominant $xy$ orbital character. We further fit the form factor obtained by FRG to real-space orbital basis pairing picture, which shows more clearly the differences between different iron-based superconductors.

• Received 26 February 2010

DOI:https://doi.org/10.1103/PhysRevB.81.184512